Does Creo Ignem fire disappear?

I'm dealing with an Ignem specialist for the first time, and I'm sure this issue must have been discussed before but I've searched through the forum and found nothing. If a magus casts a spell to create fire on a pile of wood, with a duration of diameter, what happens after 2 minutes?

Does the fire disappear completely? Or is it that only the "original" fire disappears and the wood has now been lit and is burning naturally so continues to burn? Similarly, does someone set on fire with a momentary Creo Ignem attack spell continue to burn?

And more broadly, what is the difference between a fire created with duration momentary, diameter, sun and moon? It feels to make sense that they would all continue to burn until they were put out or ran out of fuel, but then what's the point in the duration? Do they come back to life if extinguished before the duration ends? Do they burn even without fuel?

Regarding creating heat, RAW implies that heat does not disappear when the spell ends, but that heat created with momentary duration will remain (though presumably gradually the object will return to normal temperature) - see Heat of the Searing Forge, ArM5 p 140.

Have I missed something obvious in the rules that covers all this?

The encompassing rule is here (ArM5 p.77 Techniques Creo (Cr) "I create"): "Magically created things last for the duration of the spell, but their effects last indefinitely." So if the Pilum of Fire has set the pile of wood aflame, that burning pile of wood remains burning even if the spell's duration expires: until the natural fire caused by the spell has reduced the wood to ashes, gets doused by a rainstorm or otherwise ceases to burn.
A Pilum of Fire with a longer duration exists longer as a magical fire: so requires other means to put out during that time.


Create a Ring duration CrIg spell and you can have a campfire without needing wood, anywhere you can draw a circle.
Anywhere you can draw a circle, including a damp mud flat or snow field. Of course, the side effects of the heat of the fire might cause environmental effects that delete the circle (eg melt the snow field)


To answer more concretely:

The latter. Note the fire's intensity (and hence damage) may be different from the original spell's.

If the spell was enough to really set him on fire, then he continues to burn. If the spell just hit him with fire damage, it may not have actually set him on fire.

No, the magical fire continues to burn regardless of fuel, and cannot be put out (without countering the magic).

Yes. The magical effect was to heat the object. That object remains hot when the spell ends. It is the heating that stops, the heat created remains.


To add to this, in normal circumstances I assume that a momentary Pilum of Fire is not enough to set a target alight. That might change if the thing (or its immediate surroundings) was really flammable, though - parched undergrowth, desiccated (walking) corpse...Sensible Flambeau learn learn PeIg (or CrAq) spells as well as CrIg ones.

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I am not saying you can't come up with an exception, but I tend to think that momentary spells do not cause a fire unless designed to do exactly that. Your Pilum of Fire hitting really flamable material, would IMHO immediately incinerate it. It is an instant damage spell, so that is what it does, and it does not have time to do anything else.

But at the end of the day, every circumstance is unique, and so it is a judgement call.

«Sensble Flambeau», isnt't that a very rare breed? Or is that only as PC they are rare?

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Yes - my main thoughts on this are about the person's clothes. If immediately incinerated you suddenly have a charred, naked person. And if not, perhaps the clothes are set alight (I don't think it would take a very intense fire to light wool, linen or cotton)

Thanks for all the responses, it has cleared things up for me.

Neither wool nor cotton burn easily. Isn't wool the standard clothing for fire fighters?

But I do not think intensity is the issue. Duration is. It takes time to ignite cotton and wool. (I have little experience with linen.) A glow can burn a hole in cotton trousers without igniting it, contrary to polyester and other synthetics which may be ignited or incinerated quickly and easily.


So I'm thinking under the Creo Ignem guidelines cotton and wool probably fall under "slightly flammable (like leather or damp wood)". I imagine they're not as hard to burn as leather, but it sounds like they're harder to burn than the next category down of "flammable materials (like dry wood or charcoal)"

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It's rather hard to make wool burn.
Easily acccessable linkie : "the temperature must reach 570–600°C before wool will ignite", which obviously is rather above the 325°C melting point of lead, and even above classic "glowing red metal" (at 525°C and above).

I would probably consider wool "not flammable" for this purpose.

EDIT: fixed typos and missing words :hot_face:


People in general really don't catch fire very well until long after they are dead. Pilum of Fire is effectively cooking people to death. OTOH clothing can burn, but a Pilum acts like a javelin, so it's not contacting much clothing and most natural fibers don't burn very well and would easily be extinguished with some vigorous slapping.

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Wow - I didn't know it was harder to burn wool than lead! That's quite amazing. Thanks.

well, it is harder to burn wool than to melt lead. burning lead would be a whole different feat.
Part of the issue is that even with a really hot source it takes time for a target to absorb that heat and ignite. I'd recommend links to thermal insulation, specific heat and R factors, but those simply would not apply in an ars magica world, and most people in an ancient world will not have experience with temperatures hot enough to effectively overwhelm the normal delay to ignition getting a fire to 10,000 degrees simply wasn't done (the hottest forges used granite for their external structure, got up to 1000 F, were exceedingly rare and took a long time to get up to temperature), so from the perspective of medieval experience, some things take time to light no matter how hot the fire.


For game balance a momentary ignem spell causing ongoing fire is a bit strong, however, as shown by others, not only does game balance suggest no, so does physics.

If your ignem specialist has a fascination in seeing things put on fire, there's coat of flames.

Your ignem specialist could branch out. Creeping oil, which if they have any idea of his fire skills, would be terrifying, sets up later burn.

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I was reading it and nodding at 10,000 degrees, and then realized you were talking Fahrenheit and that I have no idea what that means....

I recently had the above discussion with a player, and he brought up Creeping Oil to allow himself to set up a mighty fire quickly. I think the spell's damage is ... weird, to put it mildly. The rest of the CrAq guidelines are all about setting up damage-by-magnitude guidelines very much in-line with other TeFo combos - and then this spell comes out of nowhere with a +12 fire damage on the first round. I have no idea why the authors, in their infallible wisdom, decided a natural burning oil explodes with the heat intensity of molten lead (also +12) and then fizzles to nothing.

Before he brought up this spell, I relied on the WONDERFUL paper, " Characterization of Stovetop Cooking Oil Fires"

(check out the gorgeous Figure 4, with the pictures of the gradually-enflamed stove-top... you gotta love science!)

according to which it would take a few minutes for cooking oil to reach max temp, which will then be a bit weaker than the heart of a raging bonfire (which is +10 by RAW).

Speaking of which - the fire damage in ArM really lacks examples. We have torch at +5, and bonfire at +10. And that's it. Art & Academe adds greek fire at +15, but that's not too informative. I added "burning trebuchet charge" (also alchemical) at +20, and then there is the magical "ball of abysmal flame" at +30.


Burning lead is ... indeed a different feat.
That said, there is such a thing as Lead(II) Oxide), which means you can, infact, oxidize lead. And since fire is - chemically speaking - just oxidization, though usually a particularly exothermic reaction, I suppose you could talk about lead burning :wink:

The fire starting 15th of April 2019 in the roof structure of Notre Dame de Paris affected the over 400 metric tons of lead there: most just melted, some, however, oxidized and spread to the surroundings, raising lead levels there to dangerous numbers.
You can take that well published conflagration as an example, if you wish to treat hot log-fires involving large amounts of lead in your saga.

They didn't. They set it at boiling water. And then note that the spell specifically covers the entire person's body with oil, which multiplies damage by 4. (Note that CrIg damage is fixed by magnitude, whether you want a weaker fire over a whole body or a more intense fire at an isolated spot, so the CrIg magnitudes behave differently.)

Are you reading what you quoted? It doesn't say this at all. Yes, look at figures 6 or 9 and you see a couple minutes. But that is for pan C. Now look at figure 8. Pan D only takes about halve a minute, and that depth is still roughly 7 mm or so. Why? There are geometric issues going on here. Now, the linear fit they drew here is pretty questionable; it looks like a power law with a power between 0 and 1, but there are only three points so there is no good way to fit to it. Regardless, the spell saturates enough cloth to cover a person, and the typical sheet of cloth is well under 7 mm thick. So the graph indicates it should take well under 30 seconds to reach its highest temperature. Just how long is hard to say without knowing more. if we estimate 2 mm, then that graph would indicate in the ballpark of 6 s.

I'm not arguing the spell has the right level of damage, nor that two rounds is the right amount of time, nor that halving the damage from the first to the second round and then nothing the third round is correct. But the spell doesn't seem nearly so off as you're indicating.